Our laboratory has been focused on defining the biologic properties of a cytokine that is now called human recombinant histamine releasing factor (HrHRF). HrHRF activates basophils, eosinophils, and inhibits T cell production of certain cytokines. Recent data suggest there is an additional extracellular molecule that interacts with HrHRF. Furthermore, we have uncovered an explanation for the apparent hyperreleasability of HrHRF-responder (R) donors' basophils. This application will investigate the interaction of HrHRF with an extracellular molecule as well as define the nature of hyper-releasability in HrHRF-R donors' basophils. There are 3 specific aims. Aim IA. We hypothesize that HrHRF has a unique receptor on the cell surface. IB: We further hypothesize that signaling through the HrHRF receptor involves protein tyrosine phosphorylation. We will identify this receptor and clone it, as well as determine the specific signaling pathways. In aim 2A, we will further characterize the HrHRF-R basophil. We have published a negative correlation between the expression SHIP and histamine release to HrHRF. We hypothesize that signal transduction elements downstream of SHIP will demonstrate characteristics distinct from the same pathways in HrHRF-NR donors. Aim 2B will investigate the effects of sensitization with IgE from HrHRF-R donors. Finally, Aim 3 will dissect the regulatory mechanisms of SHIP expression and clinical correlates. In Aim 3A, we hypothesize that over-expression of SHIP in HrHRF-R donors' basophils will change the phenotype to an HrHRF-NR. We will test this by transducing SHIP into basophils using HIV-TAT protein. We further hypothesize that exposure to a natural allergen and/or cytokine can alter the levels of SHIP protein. In aim 3B and 3C, we will follow levels of SHIP protein by culturing basophils in the presence of cytokines and follow donors in and out of a naturally occurring allergy season. In summary, identification of a receptor for HrHRF will be important to identify a blocking molecule that will inhibit the extra-cellular actions of HrHRF on inflammatory cells. Furthermore, it is important to dissect the hyper-releasable phenotype of HrHRF-R donors and establish that SHIP may play a "gatekeeper role" in human basophils. [unreadable] [unreadable]